Draft: Draft: Refactor GitlabNote adapter to use system-note lifecycle (alternative to !235039)

Thomas Schmidtrequested to merge
ts/migrate-mention-trigger-to-message-adapter-system-note-variant into master

What does this MR do and why?

This is an alternative approach to MR !235039 (closed) (!235039 (closed)) for side-by-side comparison. See the proposal comment at !235039 (comment 3395313223) for the full rationale and trade-offs.

Summary

Refactors Ai::Messaging::Adapters::GitlabNote to use a system-note lifecycle that mirrors the already-merged GitlabDuoNote adapter, replacing the editable progress-note UX (🔄 Processing → ✅ has started).

Lifecycle change

Phase MR !235039 (closed) (progress note) This MR (system note)
on_request_received Creates a 🔄 progress note Validates project/noteable/note exist; returns ServiceResponse.success
on_flow_started Edits progress note to ✅ Posts a duo_mention_started system note; stores started_note_id
deliver_result Posts reply note Destroys started system note, posts reply note
deliver_error Posts reply note Destroys started system note, posts error reply note

Key changes

  1. GitlabNote adapter refactored to mirror GitlabDuoNote's lifecycle:

    • manages_system_notes? = true suppresses default CreateWorkflowService system notes
    • on_flow_started posts a duo_mention_started system note via IssuablesService, authored as the configured service account
    • deliver_result/deliver_error destroy the started system note before posting the reply

  2. duo_mention_started lifted from MergeRequestsService to IssuablesService so it works for Issue, MR, AND WorkItem noteables (not just MR). The i18n key is renamed from DuoCodeReview| to Ai| since the message is no longer code-review specific.

  3. GitlabDuoNote updated to call IssuablesService#duo_mention_started instead of MergeRequestsService#duo_mention_started (one-line change to which service it instantiates).

  4. WorkItem support: GitlabNote supports Issue, MR, AND WorkItem — a key feature vs. GitlabDuoNote which only supports Issue+MR.

Consolidation follow-up

GitlabNote and GitlabDuoNote remain separate classes in this MR. Consolidation (e.g., GitlabDuoNote < GitlabNote inheritance) is a deliberate follow-up so each step is easy to review.

References

Screenshots or screen recordings

Before (MR !235039 (closed)) After (this MR)
🔄 Processing note appears immediately, then updates to ✅ has started started mention session N system note appears, disappears when final reply arrives

How to set up and validate locally

  1. Set up a service account and flow trigger for @mention flows (see MR !235039 (closed) for setup instructions)
  2. @mention the service account in an issue comment, MR discussion, or work item comment
  3. Observe: no progress note appears immediately (unlike !235039 (closed))
  4. When the flow starts: a system note started mention session N and will let you know when it's finished appears
  5. When the flow completes: the system note disappears and the final reply note appears in the discussion

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